Updated on February 28, 2018. This article has been updated to clarify descriptions of the scholar Judy Chu’s work.

In the aftermath of a school shooting, one question always stands out: Why did he—it’s almost always a he—do it? Such an event, and its male perpetrator, draws attention to an awful truth lurking behind the “crazy” outburst: Male violence isn’t a one-off, anomalous occurrence, but one more event in a steady drone of violence in homes, schools, and neighborhoods.

In 2014, the University of Alabama criminologist Adam Lankford examined a database of mass killings that occurred from 2006 to 2012. Of the 308 killers, 94 percent were male. Separately, Mother Jones compiled a list from 1982 to today; they found that of 93 shooters in 2014, 97 percent were male. In other violence categories, boys have a higher rate of assault than girls and a suffer higher rate of injury from assault. They are also more likely to report being in a fight in the past year and far more likely to be a homicide victim. In fact, homicide has become the leading cause of death for young African American males.

Another display of male violence recently received public attention. One week before the massacre in Parkland, Florida, photos of a woman with a black eye—allegedly the result of abuse by her then-husband, a senior White House staffer who’s since resigned—were circulated on social media and in news outlets. As with mass shootings, violence directed toward an intimate partner is more commonly perpetrated by males. The bottom line is that interpersonal violence of all kinds is largely a male phenomenon. Whether it is physical bullying, fighting, or more severe forms of violence, boys account for a disproportionate amount of both perpetrators and victims.

Like wallpaper, violence has become an unfortunate backdrop to contemporary life. But its drone cannot be completely ignored. I went to Charleston, South Carolina, to view the eclipse last summer, enjoying my first visit to a lovely town with a rich history, and stayed just around the corner from the Emanuel AME Church. Each time I walked past this historic place of worship, my mind involuntarily conjured images of Dylann Roof climbing its stairs and entering its open doors to sit, smiling wanly at the welcoming congregants, biding his time.

Why are men—young men with their whole life before them—so pulled toward violence? In TheNew York Times, the comedian Michael Ian Black pondered the connection between such flare-ups of male violence and how boys are being “left behind … trapped in the same suffocating, outdated model of masculinity.” Feeling desperate and frustrated, males have “only two choices: withdrawal or rage,” he wrote.

Boys’ relationship with violence begins as early as childhood. The Stanford scholar Judy Chu, whose work has focused on males’ psychosocial development, conducted a study in which she embedded with a small group of 4-year-old boys from largely middle-class families at a co-ed independent school outside Boston, interviewing and observing them for two years.*In a 2014 book based on the study, When Boys Become Boys, Chu wrote that when she first encountered the students, she “didn’t know what to make of the boys’ rowdy, rambunctious, and seemingly aggressive behavior.”** One boy mimicked a gun with his hand and pretended to shoot her when she looked at him. She turned her eyes away, unsure how to respond.

Chu realized that her initial reaction to the boy’s aggressive play might create a barrier to his connecting with her, and she tried to relax and “enter” his world. Shortly after the first incident, as she was reading to another child in the corner of the classroom, the boy shooter approached her and again aimed and pulled the trigger on her. This time, in an effort to engage with him, Chu responded “by smiling and shooting back at him.” But the boy corrected her: When he shoots her, she is supposed to fall dead.

In the first year of her study, the boys proved to be nimble in their relationships: attentive, authentic, direct, empathic. But by the second year, Chu had witnessed how each had realized in his own way that performing conventional types of masculinity was now the only way to satisfy the “hidden” requirement to fit himself into societal norms. The boys asserted these manly bona fides by favoring toys stereotypically designed for males, carefully distancing themselves from girls in their play and dress, and adopting attitudes of toughness and stoicism. The same boys who would sit in Chu’s lap with carefree abandon would also try out tough-guy personas and gang up on others.*** By age 6, these changes in their public behavior, which Chu regarded as examples of “resistance for survival,” had the effect of masking their authentic selves from the world.

According to Michael Kaufman, an author and gender-equality advocate, whose work focuses on boys and men, three strands weave together to form the fabric of male violence: violence toward women, violence toward others, and violence toward oneself. In the sense that many mass shootings end with the assailant turning his gun on himself, these events represent, in the view of the sociologists Rachel Kalish and Michael Kimmel, “suicide-by-mass murder.” Their notion underscores the connection between hurting others and hurting oneself: Hurt people hurt people.

In Chu’s study, the top dog in the male hierarchy, the boy willing to go furthest in swagger and tough talk, urged the other boys to form the “Mean Team” and “to bother people”—specifically girls. The boys, despite inner doubts, felt pressured to participate once their leader insisted. His “aggressive behavior and tendency to bully his peers made him a force to be reckoned with,” Chu noted. To keep their place in the group, and to avoid being targeted, humiliated, or excluded, the other boys joined the Mean Team, though in Chu’s observation they felt conflicted about it.

Social scientists have known for decades that trajectories toward violence begin early in a boy’s life. The Commission on Violence and Youth of the American Psychological Association confirmed in a 1994 report, titled “Reason to Hope,” that patterns of violence, once established in childhood, endure well into adulthood. The Stanford psychologist Albert Bandura wrote, “People are not born with preformed repertoires of aggressive behavior. They must learn them.”

Parents and others routinely observe young boys being schooled in aggression and violence. Sometimes I stand at the edges of a school playground alongside teachers and other adults and we watch the boys, unleashed from desk duty, going wild. They jump on one another, compete with one another, push one another around. It’s mostly always in high-natured exuberance and fun, but often an argument erupts and a boy gets angry for some reason and loses it, and someone gets hurt. High-natured play, even when tempers flare, is not unusual or really a problem.

But unfortunately, neither the boy who lashes out in anger nor the one on the receiving end is likely to have sufficient opportunity to recover fully from the conflict. Social conventions impel boys to move on, be strong, suck it up. And most boys find no one willing or able to listen to their upsets anyway. Instead, they resolve hurt feelings with a default strategy: They distance themselves from their upsets. On the outside, boys put on a mask; on the inside, many lose touch with their emotions and, in the words of George Orwell, “grow to fit” the masks they wear. In this way, boys’ experiences of aggression and force develop into interpersonal habits.

The good news, however, is that times are changing and boyhood, so tied to what society has thought it requires of males, is likely to change as well. The psychologist Jean Twenge researched members of “iGen,” whose cellphones are virtual extensions of their voices and minds, and found that they were headed toward what she described in The Atlantic last year as “the worst mental-health crisis in decades.” In a piece in TheNew York Times Magazine last fall, the Emerson College professor and writer Benoit Denizet-Lewis described a new age of anxiety afflicting teenagers, due in part, it seems, to the use of technology. Under such conditions, it is not surprising that young men are responding with reordered priorities. Reporting on the results of a “masculinity audit” in the United Kingdom, Rachel Moss noted that 18- to 29-year-old males “view their mental health as more important than their physical health.”

When I meet with high-school boys, I notice how different they are from those of my generation, that what they face as males is far from my experience. Ideas about boyhood that persisted for generations are beginning to recede. At a time when researchers such as Stephanie Coontz and David Autor report that fewer Millennial women are interested in traditional forms of marriage, even to have children, younger men are looking forward, not back. The sociologist Michael Kimmel, in his recent book, Angry White Men, suggested that young fathers who spend more time with their children, some even choosing to be stay-at-home dads, represent something more than simply wanting better work-family balance. Their choices suggest that men have new possibilities.

Human nature is like the planet’s ecosystem. Each has hard and fast realities that can be ignored only at a significant cost. In children’s development, there are undeniable limits to how much their instincts and needs—for connection, emotional expression, safety—can be neglected before there’s a reckoning. Male violence is a sign that something is out of whack—not merely with one young man or another, but more generally with the model of boyhood available to our sons. Male violence is not a new problem, but there’s a sense today, as students at Marjory Stoneman Douglas challenge inaction on guns, that the public mind has reached its own limit to rationalize and resign itself to boys’ bad behavior.

Male violence is rooted in the conditions provided for boys: In compelling them to distance themselves from those they depend on, shut down their necessary emotions, and harden themselves in an effort to feel no pain, male conditioning violates boys’ basic natures and sets them up to act out in ways that hurt others. Inadvertently, lessons intended to toughen boys in preparation for manhood make them lonelier, less adaptive, and less resilient. Like a one-trick pony: domination, anger, and aggression all the time. As the psychologist James Garbarino explained in Lost Boys, his book about male violence, even confused young men such as Nikolas Cruz might be kept in check by an anchoring relationship—“someone absolutely committed to the child and to whom the child feels a strong positive attachment.”

I am inspired by the young men I meet with in an emotional-literacy program at a school outside Philadelphia. Because they are encouraged to discuss topics relevant to their lives—relationships of all kinds, anxiety, sex, pornography—they readily take off their masks. As they share their authentic selves with one another, they create a brotherhood that is honest and warm—a bond that encourages participants to admit their shortcomings (including times they have hurt others) and discourages them from pretending that they never feel hurt, scared, or weak.

I don’t have to do more than give these young men permission to be themselves. Even those who have, like most of us, taken their anger or desperation out on someone else find themselves owning up to their lapses and working their way back to their human family.

*This story originally stated that Chu's study was of affluent families.

** It also incorrectly reported that Chu was a parent at the time of her study.

*** It also incorrectly reported that the boys would play with Chu's hair. We regret the errors.

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Michael C. Reichert is a psychologist and the executive director of the Center for the Study of Boys’ and Girls’ Lives.